“He’s a longtime TV veteran who’s appeared on shows like ‘Judging Amy’ and ‘My Name is Earl,’ but Melissa is overshadowing him.

“Making matters worse, Billy thinks she’s reveling in it, and the tension between them is growing.”

The rotund comedian, 42, stars as police officer Mike Biggs, and former “Gilmore Girls” star Melissa, 41, plays teacher Molly Flynn-Biggs in the hit CBS show about a couple who met at an Overeaters Anonymous meeting and face romance and their size with hilarity.

“The last straw for Billy was when the Emmy nominations were recently announced and he was left out again while Melissa got another nod,” said the insider. “Billy is worried that Melissa is getting way too big for her britches, and it didn’t help that at last year’s Emmys she was crowned with a tiara. Billy’s ego is bruised.”

The actor didn’t help matters when he failed to phone Melissa with congratulations after the Emmy nominations were announced, said the set insider. “Right now there’s a rift because Mike can’t stand Molly.”